Features of cartilaginous fishes
(i) Cartilaginous endoskeleton is present,
(ii) These are mostly marine, poikilothermic animals.
(iii) Notochord is persistent throughout life,
(iv) Placoid scales are present.
(v) Heart is two chambered with one auricle and one ventrical. .
(vi) Tail fin is always heterocercal.